OUTCROP-SCALE FAULTS IN THE EASTERN CENTRAL RANGE OF TAIWAN, A KINEMATIC LINK BETWEEN PLASTIC STRAIN AND CONTEMPORARY SEISMICITY

Taiwan is the result of the Luzon volcanic arc colliding with Eurasia’s passive margin. Taiwan’s Central Range has been undergoing rapid exhumation over the past 1 Ma and uplifting at a rate of up to 8mm/yr. In an attempt to provide constraints for modeling purposes, we set out to document the geometry and kinematics of the plastic to brittle transition of the metamorphic core. The exposed fabrics and structures in the Central Range show the geometry and kinematics of plastic and brittle structures, that likely reflect NW-directed shortening. Here, we specifically focus on recent field observations of outcrop-scale faults in a seismotectonic context. Preliminary findings suggest that the faults of unknown age broadly accommodate deformation that is kinematically similar to contemporary seismicity. Fault data and focal mechanism solutions in the eastern Central Range accommodate sub-horizontal NE-SW stretching and oblique normal faulting. Comparing the brittle deformation to older plastic structures, we argue veins are the transition between the plastic and brittle regimes. The veins show mutual cross-cutting relations with young metamorphic foliations and show the same NE-SW stretching in exposed outcrops >100 km along strike. Although we have limited fault slip data, we are aware that many rich unpublished fault data sets have been amassed in this region. Given the ephemeral nature of exposures in this area, we suggest there is an opportunity to integrate data sets to robustly constrain the kinematics of deformation here. We suggest that NE-SW stretching may reflect kinematics during the transition from plastic to contemporary brittle strain. These constraints are important in any attempts to understand Taiwan’s exhumation history.